Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device including a process of processing a substrate, and relates to a substrate processing apparatus.
Description of the Related Art
As one of processes in a manufacturing process of a semiconductor device, there is a thin film formation process of forming a CVD thin film such as a silicon nitride film (Si3N4 film) or the like, on a substrate such as a semiconductor wafer or the like, with use of a thermal chemical vapor deposition method (thermal CVD method). The thin film formation process using the thermal CVD method is performed by supplying a processing gas to the inside of a processing chamber into which the substrate has been loaded. The purpose of the thin film formation process is to form a thin film on a surface of the substrate. However, practically, a deposited material containing thin films can sometimes be adhered to a portion other than the surface of the substrate, for example, an inner wall of the processing chamber, or the like. Such a deposited material is cumulatively adhered every time when the thin film formation process is performed. When the thickness of the deposited material reaches or exceeds a certain thickness, the deposited material peels from the inner wall, or the like, of the processing chamber, which may cause generation of foreign substances (particles) in the processing chamber. Accordingly, it is necessary to perform cleaning of the inside of the processing chamber and members in the processing chamber by removing the deposited material every time the thickness of the deposited material reaches a certain thickness.
Conventionally, a wet cleaning method of detaching a reaction tube constituting the processing chamber from the substrate processing apparatus, and then removing a deposited material adhered to the inner wall of the reaction tube is removed in a washing tank containing HF (hydrogen fluoride) aqueous solution, as a mainstream method of removing a deposited material. However, recently, use of a dry cleaning method which does not require detaching the reaction tube has been increasing. For example, a dry cleaning method of supplying a gas mixture in which HF (hydrogen fluoride) gas or H2 (hydrogen) gas has been added to F2 (fluorine) gas is supplied to the inside of the processing chamber and other methods are known (for example, see Japanese Patent Application Laid-open No. 2005-277302, Japanese Patent Application Laid-open No. 2005-317920, and Japanese Patent Application Laid-open No. 2007-113778).
However, when the above-described dry cleaning is performed, the film formation speed (film formation rate) is sometimes decreased in the thin film formation process which is immediately after the dry cleaning. In order to prevent decrease in the film formation rate, a method is also conceivable which makes the inner wall, or the like, of the processing chamber flat by supplying the inside of the processing chamber with a gas mixture in which HF gas or H2 gas has been added to F2 gas immediately after the dry cleaning. However, in this method, the HF gas which has been added, or HF gas generated by the reaction of F2 gas and H2 gas sometimes causes metallic contamination due to corrosion of a metal member in the processing chamber or breakage of a quartz member in the processing chamber due to erosion.